In-situ biaxial texture analysis of MgO films during growth on amorphous substrates by ion-beam-assisted deposition

We used a kinematical electron scattering model to develop a RHEED based method for performing quantitative analysis of mosaic polycrystalline thin film in-plane and out-of-plain grain orientation distributions. RHEED based biaxial texture measurements are compared to x-ray and transmission electron microscopy measurements to establish the validity of the RHEED analysis method. MgO was grown on amorphous Si3N4 by ion beam-assisted deposition (IBAD) using 750 eV Ar+ ions and MgO e-beam evaporation. The ion/MgO flux ratio was varied between 0.66 and 0.42. In situ RHEED analysis reveals that during nucleation the out-of-plane orientation distribution is very broad (almost random), but narrows very quickly once well-oriented grains reach a critical size. Under optimal conditions a competition between selective sputtering and surface roughening yields a minimum out-of-plane texture at about 100 angstrom, which degrades with increasing film thickness. The narrowest in- plane orientation distribution (5.4 degrees FWHM) was found to be at an ion/MgO flux ratio between 0.55 and 0.51, in good agreement with previous experiments. The systematic offsets between RHEED analysis and x-ray measurements of biaxial texture, coupled with evidence that biaxial texture improves with increasing film thickness, indicates that RHEED is a superior technique for probing surface biaxial texture

Interview with Lydia Groves

An interview with Lydia Groves regarding her experiences in a one-room school house.https://scholars.fhsu.edu/ors/1063/thumbnail.jp

In-situ biaxial texture analysis of MgO films during growth on amorphous substrates by ion-beam-assisted deposition

We used a kinematical electron scattering model to develop a RHEED based method for performing quantitative analysis of mosaic polycrystalline thin film in-plane and out-of-plain grain orientation distributions. RHEED based biaxial texture measurements are compared to x-ray and transmission electron microscopy measurements to establish the validity of the RHEED analysis method. MgO was grown on amorphous Si3N4 by ion beam-assisted deposition (IBAD) using 750 eV Ar+ ions and MgO e-beam evaporation. The ion/MgO flux ratio was varied between 0.66 and 0.42. In situ RHEED analysis reveals that during nucleation the out-of-plane orientation distribution is very broad (almost random), but narrows very quickly once well-oriented grains reach a critical size. Under optimal conditions a competition between selective sputtering and surface roughening yields a minimum out-of-plane texture at about 100 angstrom, which degrades with increasing film thickness. The narrowest in- plane orientation distribution (5.4 degrees FWHM) was found to be at an ion/MgO flux ratio between 0.55 and 0.51, in good agreement with previous experiments. The systematic offsets between RHEED analysis and x-ray measurements of biaxial texture, coupled with evidence that biaxial texture improves with increasing film thickness, indicates that RHEED is a superior technique for probing surface biaxial texture

A cortical potential reflecting cardiac function

Emotional trauma and psychological stress can precipitate cardiac arrhythmia and sudden death through arrhythmogenic effects of efferent sympathetic drive. Patients with preexisting heart disease are particularly at risk. Moreover, generation of proarrhythmic activity patterns within cerebral autonomic centers may be amplified by afferent feedback from a dysfunctional myocardium. An electrocortical potential reflecting afferent cardiac information has been described, reflecting individual differences in interoceptive sensitivity (awareness of one's own heartbeats). To inform our understanding of mechanisms underlying arrhythmogenesis, we extended this approach, identifying electrocortical potentials corresponding to the cortical expression of afferent information about the integrity of myocardial function during stress. We measured changes in cardiac response simultaneously with electroencephalography in patients with established ventricular dysfunction. Experimentally induced mental stress enhanced cardiovascular indices of sympathetic activity (systolic blood pressure, heart rate, ventricular ejection fraction, and skin conductance) across all patients. However, the functional response of the myocardium varied; some patients increased, whereas others decreased, cardiac output during stress. Across patients, heartbeat-evoked potential amplitude at left temporal and lateral frontal electrode locations correlated with stress-induced changes in cardiac output, consistent with an afferent cortical representation of myocardial function during stress. Moreover, the amplitude of the heartbeat-evoked potential in the left temporal region reflected the proarrhythmic status of the heart (inhomogeneity of left ventricular repolarization). These observations delineate a cortical representation of cardiac function predictive of proarrhythmic abnormalities in cardiac repolarization. Our findings highlight the dynamic interaction of heart and brain in stress-induced cardiovascular morbidity

Metabolic potential of uncultured bacteria and archaea associated with petroleum seepage in deep-sea sediments

Little is known about the microbial ecology of the deep seabed. Here, Dong et al. predict metabolic capabilities and microbial interactions in deep seabed petroleum seeps using shotgun metagenomics, sediment geochemistry, metabolomics, and thermodynamic modelling

Does Conservation Planning Matter in a Dynamic and Uncertain World?

We show that while comprehensive reserve network design is best when the entire network can be implemented immediately, when conservation investments must be staged over years, such solutions actually may be sub-optimal in the context of biodiversity loss and uncertainty